1. Field of the Invention
This invention relates to the art of vacuum pre-coat filtering to produce solids capable of being incinerated for their heat value and recovery of non-combustible solids. Specifically, the invention deals with rotary vacuum filtering apparatus containing a coating layer on the filter drum screen of a combustible non-fibrous particulate filter aid, preferably charcoal, which forms an efficient filter bed, is capable of being scraped from the bed in thin film form with the filtered out solids thereon and is capable of being incinerated eliminating heretofore necessary disposal expense.
2. Description of the Prior Art
Heretofore known pre-coat filter aids have been of the non-combustible inorganic type such as diatomaceous earth, perlite, and the like or of the combustible type such as cellulose fibers. The incombustible filter aids prevent recovery of heat values in the filtered out solids because of their silicate origin which forms glass upon combustion of any combustible slurry solid admixed therewith and also prevents recovery of valuables in the solids. The combustible cellulose type filter aids are fibrous in nature and cannot be scraped evenly from the filter bed, thereby reducing their efficiency. The fibers are somewhat compressible and cannot form a dimensionally stable filter bed.
It would, therefore, be an improvement in the art to provide a filtering apparatus having a coating of efficient, combustible filter aid free from non-combustible ingredients and fibers and forming a dimensionally stable filter bed on the drum of a rotary vacuum filter machine.